The present invention relates to a device for use with shirred tubular casing stuffing machines for stuffing casings having a uniform diameter. It particularly relates to a device which is adapted to be mounted on the stuffing horn of such machines for uniformly controlling the filling of shirred tubular casings by pre-expanding the casing prior to filling and controlling the draw-off speed of the casing from the stuffing horn.
It is known to use shirred tubular casings of synthetic, semi-synthetic, or natural materials for packaging food products, such as meat, in the form of sausages. The shirred casings utilized for this purpose, also called "sticks" or "hollow rods" by those skilled in the art, are produced by shirring and compressing long tubes of casing in the direction of their longitudinal axis to approximately 1 to 3% of their original length. In order to fill the shirred casing with sausage composition or other food product, conventionally one end of the shirred casing is first closed, and then the shirred casing is normally fit onto the stuffing horn of a sausage machine. A sausage mixture is next forced, under pressure, through the stuffing horn into the casing, by which the shirred casing is continuously deshirred. After a certain predetermined length of the casing has been filled, the filled sausage casing is subdivided into cylindrical sausages which are then tied off and closed.
It is desirable that the cross-section of the sausages thus produced remains constant over their entire length. Optimum filling of the tubular casing requires that a uniform diameter, the size of which is dependent upon the particular casing utilized or the length of the sausage, be maintained over the entire length of the casing. If the casing is overstuffed, it may burst, whereas an insufficiently filled sausage displays a wrinkled surface.
Heretofore, the prior art has developed several devices for uniformly controlling the diameter of the tubular casing during filling with sausage mixtures or other food products. Thus, it is conventional to fit to the opening of the stuffing horn of the sausage machine a calibrating means which prestretches the casing to be filled by pressing against the inside wall thereof. Due to this pressure, frictional forces are developed between the calibrating means and the inside wall of the casing by which the withdrawal of the casing from the stuffing horn is slowed down (U.S. Pat. No. 3,457,588). Suitable calibrating means which have been heretofore used in the prior art, for example, comprise resilient fingers disposed at the rim of the opening of the stuffing horn, which are produced by forming slits therein (U.S. Pat. No. 3,264,697). These fingers press against the internal wall of the casing and thus enlarge it. By drawing the casing over these fingers during the filling process, a frictional resistance occurs which controls the draw-off speed of the casing from the stuffing horn. This device has the disadvantage, however, that the frictional resistance cannot be adjusted for use with different sized casings. Moreover, it involves the risk that the casing may be damaged by the outspread fingers.
It has also been proposed to pre-pack the shirred tubular casing with a calibrating disc and to attach this combination to the stuffing horn prior to the filling operation (U.S. Pat. No. 4,007,761). The calibrating disc is disposed within an unshirred section of the casing and has an outer perimeter which is preferably larger than the internal circumference of the unshirred casing. During filling, the casing is drawn over the calibrating disc and is thereby stretched. In this device, the calibrating disc must consist of a non-resilient material in order to prevent its diameter from being altered by the pressure exerted by the casing in contact therewith.
The use of an inelastic calibrating disc has the disadvantage that due to variations in the circumference of the casing--which cannot be entirely avoided during manufacture--an optimum filling of the casing is not achieved. If the size of the casing is too small, the casing may be damaged by the calibrating disc or even torn off; at a minimum an undesirably high friction will occur between the casing and the calibrating disc, leading to overstuffing of the casing with sausage mixture and the inability to withstand the high pressures formed during boiling of the sausage. On the other hand, if the diameter of the casing exceeds a certain optimum size, the casing will be drawn too fast over the calibrating disc and thus will not be sufficiently filled with sausage composition.